Abstract
Dopaminergic brain structures like the nucleus accumbens (NAc) are thought to encode the incentive salience of palatable foods motivating appetitive behaviour. Animal studies have identified neural networks mediating the regulation of hedonic feeding that comprise connections of the NAc with the ventral tegmental area (VTA) and the lateral hypothalamus (LH). Here, we investigated how structural connectivity of these pathways relates to individual variability in decisions on sweet food consumption in humans. We therefore combined probabilistic tractography on diffusion imaging data from 45 overnight fasted lean to overweight participants with real decisions about high and low sugar food consumption. Across all individuals, sugar preference and connectivity strength were not directly related, however, multiple regression analysis revealed interaction of mesolimbic structure and sugar preference to depend on individuals’ BMI score. In overweight individuals (BMI: ≥25 kg/m², N = 22) higher sugar preference was thereby specifically related to stronger connectivity within the VTA-NAc pathway while the opposite pattern emerged in participants with normal BMI (BMI: <25 kg/m², N = 23). Our structural results complement previous functional findings on the critical role of the human mesolimbic system for regulating hedonic eating in overweight individuals.
Highlights
The consumption of high sugar diets is a discussed risk factor for obesity and type 2 diabetes[1]
We investigated to what extent real decisions about sweet food consumption are related to individual characteristics of white matter tracts connecting the nucleus accumbens (NAc) with the ventral tegmental area (VTA) and the lateral hypothalamic (LH), as identified by probabilistic tractography
The stronger the white matter connectivity within this mesolimbic pathway, the more individuals’ food wanting was driven by the sugar content of foods. This finding was restricted to overweight individuals while in normal weight participants, we observed a trend towards an opposite association, i.e. mesolimbic connectivity was related to less sugar wanting
Summary
The consumption of high sugar diets is a discussed risk factor for obesity and type 2 diabetes[1]. In the context of ingestive behaviour, studies on white matter tractography have reported both decreased and increased integrity of white matter tracts in obese compared to normal weight individuals[24,25], with some data indicating reduced connectivity in reward networks[25,26], while others report increased white matter integrity of accumbal circuits[24] in participants with higher BMI scores. One reason for this apparent controversy, besides genetic variability[27,28], might be the uncontrolled impact of individual eating behaviour on brain structure. Since we expected an impact of current weight status on structure-function associations, our sample included both normal and overweight individuals
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